Safety apparatus for steam boilers



March 27, 1956 H. R. RICARDO SAFETY APPARATUS FOR STEAM BOILERS FiledMay 26, 1952 .7 llllll Unted States Patent 2,739,576 SAFETY APPARATUSFOR STEAM BOILERS Harry Ralph Ricardo, London, England, assignor toNational Research Development Corporation, London, England, acorporation Application May 26, 1952, Serial No. 290,028 Claimspriority, application Great Britain May 29, 1951 5 Claims. (Cl. 122-451)This invention relates to safety apparatus for steam boilers and has foran object to provide a form of apparatus, particularly but notexclusively applicable to small boilers, which will be simple inconstruction and reliable in operation for preventing a dangeroucondition occurring in a boiler.

According to the present invention safety apparatus for a steam boilercomprises float apparatus including a float responsive to the waterlevel in the boiler, an automatic pressure-operated safety valve subjectto the steam pressure in the boiler, and means whereby the steampressure required to cause the safety valve to open is automaticallyreduced by the downward movement of the float due to a drop in waterlevel.

Since, with apparatus according to the invention, as the water leveldrops, the steam pressure required to lift the safety valve becomes lessthe escape of steam through the safety valve may constitute a warningthat the water level has dropped undesirably. Moreover the arrangementis preferably such that, if the water level falls to a dangerous degreethe float will cause the safety valve to open irrespective of steampressure and thus substantially relieve all steam pressure within theboiler, thus avoiding risk of explosion.

The invention is particularly applicable to boiler installationsincluding a feed water pump and means for automatically controlling thedelivery of feed water to the boiler by the feed water pump to maintaina substantially constant water level in the boiler, and one particularly convenient arrangement of combined feed water control andsafety apparatus according to the invention comprises float apparatusincluding a float responsive to the water level in the boiler, a feedwater pump, means responsive to movement of the float apparatus forcontrolling the delivery of feed water to the boiler in a manner tendingto maintain a substantially constant predetermined water level in theboiler, an automatic pressure-operated safety valve subject to the steampressure in the boiler, and mechanism actuated by the float apparatuswhereby the steam pressure required to cause the safety valve to open isautomatically reduced by downward movement of the float below apredetermined point due to the Water level dropping below thepredetermined level. In such an arrangement the feed water pump may bearranged to deliver water to the boiler at a pressure somewhat greaterthan that of the steam therein and the float apparatus may operate afeed water admission valve so as to open such valve when the water leveldrops below the predetermined level and to close it when it rises abovesuch predetermined level, the admission valve conveniently being in theform of a needle valve which is maintained closed against the feed waterpressure by the float apparatus when the water level is at thepredetermined level and is permitted to open when the water level dropsbelow such predetermined level.

In any case in apparatus according to the invention the reduction in thesteam pressure necessary to open the safety valve when the water leveldrops is preferably 2,739,576 Patented Mar. 27, 1956 effected byarranging the float apparatus so that when the float drops below apredetermined point the float apparatus exerts a force on the valvemember of the safety valve tending to open it.

Constructions according to the invention may vary widely according tothe type of boiler to which the in vention i applied and otherconsiderations but one construction according to the invention isillustrated somewhat diagrammatically by way of example in theaccompanying drawings, in which Figure 1 is a side elevation mainly insection of a form of boiler having associated therewith combined feedwater control and safety apparatus according to the invention,

Figure 2 shows diagrammatically the feed water system associated withthe boiler, and

Figure 3 is an enlarged view in section of the left hand end of Figure1.

In the construction shown in Figure l the boiler is of horizontalcylindrical form and comprises a circumferential wall A having externalheat transfer ribs thereon and end walls A and A the boiler beingsupported on a fire box generally indicated at B, so that the hot gasespass around it and escape through a smoke stack or the equivalentindicated at B The end wall A has mounted on it a dome like housing orchamber C the interior of which opens into the interior of the boilerthrough a central aperture A in the end wall A as shown.

An elongated float D, which as shown extends nearly throughout thelength of the boiler A, A A is arranged within the boiler and pivoted atD at approximately the centre of its length and about a horizontal axisto the forked end of an arm E the other end of which is pivoted at E ona horizontal pin within the chamber C so that the float D and arm E liftand fall with rises and falls in the level of water within the boiler A,A A

Mounted in the upper wall of the chamber C is a safety apparatuscomprising a valve member F normally pressed onto its seating by aspring F which may be adjustable in known manner to enable the pressureat which the valve blows 011? to be adjusted. The stem of the valvemember F projects vertically downwards as shown into the interior of thechamber C on an axis which lies to the side of the pivot E remote fromthe float D.

Coaxial with the stem of the valve member F but arranged in the lowerwall of the chamber C is a feed water admission valve G in the form of aneedle valve arranged within a housing G so as to control the admissionof feed water from an inlet passage H to ports G in the housing G Thefloat arm E is provided with an extension having upper and lower camsurfaces E E one of which is arranged to bear upon the lower end of thevalve member F for the safety valve while the other is arranged to bearupon the upper end of the feed water admission valve G.

The arrangement is such that normally when the float D occupies aposition corresponding to the predetermined water level within theboiler at which it is desired to maintain the water, the cam surface Emaintains the feed water admission valve G on its seat while the camsurface E is out of contact with the valve member F. If, however, thefloat D drops by a small predetermined amount due to the water leveldropping below such predetermined level, the cam surface E permits thefeed water admission valve G to move from its seat to admit feed Waterand thu restore the predetermined water level, the cam surface E stillremaining, however, out of contact with the valve member F.

If, however, the water level drops to a small degree still further, thecam surface E will act on the valve member F and tendto lift it, thusreducing the steam pressure at which the safety valvewill open.

Moreover, if the water level drops to a dangerous degree the weight ofthe float D will cause the cam surface E to lift the valve member Ffromits seatand thus relieve 'all pressure'within the boiler.

The extension carrying the cam surfaces E and E may in some cases carrya pointer visible from outside the chamber C through a transparentwindow therein or, alternatively, the pinE may be rigid with the arm Eand rock in bearings in the wall of the chamber C and project at one endfrom the chamber and carry a pointer as indicated at J moving over ascale 1 With the arrangement shown in Figure 1 the feed water pump wouldbe arranged to deliver water continuously'at a pressure somewhat inexcess of the pressure in the boiler but not sufliciently in exces tolift the valve G from its seating when maintained thereon by the float.Thus, in the example diagrammatically shown in Figure 2 a constantlydriven feed water pump K draws water from a water supply pipe K and.delivers it continuously to a delivery pipe K having two branches one ofwhich K leads through a relief valve K back to the inlet side of thepump K while the other leads to the water inlet passage H of the valveG, the relief valve K being set to open at a pressure somewhat. greaterthan the steam pressure maintained within the boiler.

A pressure gauge L may be provided on the chamber C while a water inletconnection L having a nonreturn valve therein may be provided for theadmission of Water from a hand-operated or like pump for priming theboiler when it is to be brought into use.

What I claim as my invention and desire to secure by Letters Patent is:

1. Combined feed water control and safety apparatus for a steam boilerincluding a float responsive to the water level in the boiler, a feedwater pump, mean responsive to movement of the float for controlling thedelivery of feed water to the boiler by the feed water pump so as tomaintain a substantially constant predeterminedwater level in theboiler, safety valve apparatus comprising a safety valve and meanstending to close the safety valve against the action of the steampressure in theboiler, and a connection between the safety valveapparatus and the float whereby the steam pressure at which the safetyvalve opens is automatically reduced as the water level in the boilerdrops.

2. Combined feed water control and safety apparatus as claimed in claim1, in which the weight of the float and the connection between thesafety apparatus and the float'is'such' that if" the water level dropsbelow 'a'predetermined level the safety valve is opened and maintainedopen by the said connection and the steam pressure in the boiler isthereby substantially completely relieved.

3. Combined feed water control and safety apparatus for a steam boilerincluding a float responsive to the level of water in the boiler, a feedwater pump arranged to deliver water continuously at a pressure somewhatgreater than the normal steam pressure in the boiler, feed wateradmission apparatus including an admission valve and controlling theflow of water from the feed water pump into the boiler, an operativeconnection between the float and the feed water admission apparatusserving to maintain the admission valve closed when the water level isabove a predetermined level and to permit the valve to open when thewater level drops below such predetermined level, safety valve apparatuscomprising a safety valve subject to the steam pressure within theboilerand means tending to close the safety valve against the action ofthe steam pressure, and an operative connection between the float andthe safety valve apparatus whereby when the float drops below apredetermined point the steam pressure at which the safety valve willopen is automatically reduced.

4. Combined feed water control and safety apparatus for a steam boiler aclaimed in claim 3, in which the said connection between the float andthe safety apparatus includes a part which when the float drops belowsaid predetermined point due to the water dropping below a predeterminedlevel, acts on the safety valve in a direction tending to open the valveand thus serves as means for reducing the steam pressure at which thesafety valve will open.

5. Combined feed water control and safety apparatus for a steam boileras claimed in claim 4 in which the weight of the float is such that ifthe water drops below a lower predetermined level, the said connectionbetween the float and the safety apparatus will lift the safety valvefrom its seating and thus relieve the steam pressure in the boilersubstantially completely.

References Cited in the tile of this patent UNITED STATES PATENTS103,539 Anderson May 31, 1870 1,170,044 Buckley Feb. 1, 1916 1,854,519McDonnell et a1. Apr. 19, 1932 2,189,903 How Feb. 13, 1940

